Computer Upgrade

My uncle gave me a Compaq Deskpro EP/SB,
PIII 450, Processor Speed 450/100. I want to upgrade the processor, where can I find if i can upgrade it and if so to what. I went to Compaq website they keep asking for the model and the model I have say EP/SB but on their website I have to chose EP or SB. They don’t have this series listed. Can someone help me out?